The present invention relates to a glass protective film, and, more particularly, to a glass protective film for use in a glass plate for manufacturing a liquid crystal display (LCD).
An LCD glass plate is adapted to have a cleanliness grade for thin film transistor processing. The LCD glass plate includes a glass protective film to maintain high cleanliness in the course of transporting such glass plates to a transistor processing location from a production location. If the non-adhesive performance of the second surface of the glass protective film is poor, the glass protective film has to be used together with an insert paper when the glass plate is introduced to LCD processes.
When the glass protective film is used together with the insert paper in this way, fine scratches are made on the surface of the glass plate by the insert paper, and thus quality of the glass plate may deteriorate, and also, impurities are attached to the glass plate from the insert paper. Ultimately, the glass plates having the insert papers therebetween should be cleaned before a transistor process is performed. When a cleanser is used, cleaner residues may be left behind on the surface of the glass plates.
Compared to glass plates using only an insert paper, LCD glass plates using the glass protective film attached to the surface thereof and the insert paper interposed between the glass plate and the protective film have fewer scratches on the surface thereof. When stacked glass plates are separately transported one by one under the condition that the glass protective film having poor non-adhesive performance is used and the insert paper is not used, the back glass plate may be transported with being attached to the front glass plate, and thus the number of glass plates which are broken during transport may increase. The use of the glass protective film together with the insert paper may increase the number of processes and the insert paper cost, and also dust of the paper is liable to decrease cleanliness of the LCD glass plate.
Even when slim LCD glass having a large LCD screen with a thickness of about 1 mm is carefully handled by two persons, the glass may be easily broken and thus makes it difficult to handle.
Conventional techniques for manufacturing LCD glass protective films include U.S. Pat. Nos. 5,100,709, 6,040,046, 6,387,481B1, 4,895,760, and 6,326,081B1. These patent products include a glass protective film and an insert paper. Hence, there is a need to develop a glass protective film having no insert paper. The first surface of the glass protective film having no insert paper, has to have weak adhesion to the glass plate, and the second surface thereof has to exhibit non-adhesiveness so that films or the film and the glass plate do not stick together.
Korean Patent No. 10-0776197 discloses a glass protective film having a first surface with weak adhesion to the glass plate and a second surface having no adhesion to the glass plate. The formation of the rough surface having no adhesion to the glass plate may obviate the use of the insert paper. The non-adhesiveness which enables the omission of the insert paper should be adapted to safely separately transport superimposed glass plates one by one in the proper transport speed range.
However, the aforementioned film having a rough bead surface that is able to omit the use of the insert paper is a film including a polymer powder (microbeads) attached to the second surface thereof. In the course of preparation of a polymer powder by a disk mill, the yield of normal microbeads may decrease, thus lowering economic efficiency. Furthermore, the shape of normal microbeads is irregular, and the microbeads may include cracks and removable tail or lump portions, undesirably increasing defect rates in LCD processes.
As disclosed in Korean Patent No. 10-0776197, the glass protective film having no insert paper includes a base film having a first surface with weak adhesion to the glass plate and a second surface that is a rough bead surface. The glass protective film is provided in the form of a thin film so as to facilitate the post treatment including recovery after use of the protective film. The rough bead surface is formed in such a manner that a polymer is melted by an extruder and then formed into a film, and microbeads are dropped to an appropriate density on a rotating cooling rubber roll and then attached to the second surface of the formed film without changing the distributed state thereof while the film is cooled and cured by a cooling rubber roll.
To manufacture microbeads for the rough bead surface as the second surface of the glass protective film, a low-density resin (LDPE) is prepared and pulverized by a disk mill. As illustrated in FIG. 7, the pulverized low-density resin powder has an irregular particle shape or size. To obtain the preferable normal microbeads, the microbeads are sieved using a 40-mesh screen and a 50-mesh screen, thus sorting the polymer particles having a particle size of 500˜600 μm.
When microbeads in the wide particle size range of 50˜500 μm are used to manufacture the glass protective film, the preparation yield of microbeads by a disk mill may increase but a height variation of the beads attached to the base film may increase, and thus, as illustrated in FIG. 3, the ceiling reach rate of the microbeads may be remarkably lowered to 15˜20%, undesirably significantly deteriorating the non-adhesive performance of the glass protective film. Further, even when the low-density polymer pulverized by a disk mill is sorted to a particle size of 450˜550 μm, it is difficult to completely separate fine particles and thus limitations are imposed on improving the ceiling reach rate of the beads of the rough bead surface of the glass protective film.